2019 MRU MP7 Stuck VGT?

[Christian Wagner]

Howdy Gentlemen (and ladies obviously), as the title would suggest I have a 2019 MRU with an MP7 that acts as the truck/powerplant for Putzmeister Concrete Pump. This is probably important information because this engine does  A LOT of PTO time, with low load. The engine only needs about 1350 rpm in 9th gear to run the Hydraulic pumps and it still only puts a 20-30% oscillating load on the engine maximum. This truck now has about 3800 hours on it with only 18,000 miles, it has a 10 speed manual and spends a lot of time in town. This issue I have started in the fall of 2021, I went out to do a pour and while setting up I noticed the turbo sounded louder than usual, not in actual volume but as in it sounded spooled up like it does when it goes into its "heating" mode on startup. Typically when setting up the machine it is at an idle, typically when its cool out and the truck is left idling the turbo will spool up, I don't entirely know why these things do this but I noticed they do. so I thought nothing of it, except when I went to throttle it up to get more hydraulic power it didn't come out of this mode, and the turbo spooled up a lot with rpm. It seemed as though the turbo was getting stuck in a certain position instead of varying with load/RPM. I climbed into the cab to check for CEL but there was nothing. I turned the truck off, and turned it back on and the issue was gone, all normal. The problem is, I don't believe in things that fix themselves. This happened 2-3 more times in the next week upon which time I contacted a few local mechanics and my nearest dealership and they all pretty much immediately pointed to my VGT actuator/Vanes. My normal mechanic talked me into trying some of this "C4 Turbo cleaner" which after running 2-3 tanks through (and changing my fuel filters) I didn't see an issue for almost 6 months which made me think that everybody was right and that stuff worked. Unfortunately the story isn't a happy ending, today the issue reared its ugly head but worse than ever, during a single pour it happened 3 times. Another thing id like to add is, this has NEVER happened while driving, only while in PTO or idling at the fuel island. I don't want to continue using this turbo cleaner as a Band-Aid fix, especially since I don't know what it actually is and if its robbing my engine of what little lubricant diesel already has, but I also don't want to spend money on an actuator/turbo unless I get a large consensus of mechanics telling me I should. The guys on this forum have been very helpful in the past and I know there is a wealth of information/experience here. So my questions I have for you guys, 

1. Why do you think there is NO check engine light?

2.Why does turning the truck off and back on again "Fix" it?

3.What is your genuine opinion on this issue?

4.Is there any other questions you have?

[Onyx610]

Does it cycle the sliding ring nozzle when you turn the key on? You should hear it. That’s where it does it’s check. This could be a software issue or maybe an egr. The best way to tell is have PTT hooked up for when it does do it. 

[Onyx610]

Also the fact this only happens a few times and only when pto is engaged would have me considering other options then a turbo. A lot of times people hang turbos on trucks and then find out it was something simple like a DRV, boost leak, or a sensor, etc. My suggestion would be get the truck to operating temp and do a vgt function test. 

[wiserfrombud]

These newer emissions engines do a 1000 different things to maintain temps, dpf cleanliness, particulate, Nox, and the list goes on.   Instead of worrying about how the turbo "sounds" or what it's doing at any given time, how does the truck RUN?   when you mash the throttle to the floor does it make proper boost?  Engine brake seem to function properly?  Hopefully with today's prices you somehow monitor fuel consumption, per hour I guess for your operation.  Any change?   Those are all good places to start.   Don't go down the path of chasing a problem that might not be there.  The shops will be happy to throw parts at it for thousands per visit.  

[Onyx610]

See if you can get a video of it when it does what your saying. All honesty it may be normal. I’d like to hear it. 

[Christian Wagner]

2 hours ago, wiserfrombud said:

These newer emissions engines do a 1000 different things to maintain temps, dpf cleanliness, particulate, Nox, and the list goes on.   Instead of worrying about how the turbo "sounds" or what it's doing at any given time, how does the truck RUN?   when you mash the throttle to the floor does it make proper boost?  Engine brake seem to function properly?  Hopefully with today's prices you somehow monitor fuel consumption, per hour I guess for your operation.  Any change?   Those are all good places to start.   Don't go down the path of chasing a problem that might not be there.  The shops will be happy to throw parts at it for thousands per visit.  

Sorry, I forgot to add one crucial detail, when it does this it limits my rpm to 1600.

[Mackpro]

At this point I wonder if it’s programing done by the bed company (Putz) as a safety feature and limiting RPM due to something going on with the bed ( transfer case temp) ? The Mack Body Builder online manual has lots of free info on possible parameter settings for theses types of Installz. I’ll link the page soon 

[Mackpro]

https://www.macktrucks.com/parts-and-services/support/body-builders/manuals/heavy-duty/.  Lots of good information in this link here but I swear at one time they had info on how to set up the parameters to run a driveline pump for the concrete pumpers and what possible derates there could be .